The beautiful girl, who, lolling back upon the saddlebags, commenced to chatter in French about mutual friends in Warsaw, in Moscow, and in Petersburg, was none other than Sonia Ostroff, known to every Nihilist in and out of Russia as "The Sylph of the Terror." Her slim figure, her childish face, her delicate complexion and charming dimples made her appear little more than a girl; yet I well knew how her bold, daring schemes had caused the Tzar Alexander to tremble. The daughter of a wealthy widow moving in the best society in Petersburg, she had become imbued with convictions that had induced her to join the Nihilists. From that moment she had become one of their most active members, and on the death of her mother, devoted all the money she inherited to the Cause. Many were the remarkable stories I had heard of the manner in which she had arranged attempts upon the lives of the Tzar and his Ministers; how, on one occasion, with extraordinary courage, she had taken the life of a police spy with her own hand; and how cleverly she had always managed to elude the vigilance of the ubiquitous agents of the Third Section of the Ministry of the Interior. Yet, as she laughed lightly, and pulled the rudder-line sharply, bringing us up to the steps before our hostess's house, few would have suspected Cecile Demage, the _chic_, flippant daughter of a Belgian mine-owner, to be the same person as Sonia Ostroff, the renowned "Sylph of the Terror," who spent greater part of her time in hiding from the police in the underground cellar of a presumably disused house near the Ekaterinski in Petersburg. Half an hour later we were sitting opposite each other at dinner, where she shone brilliantly as a conversationalist. Several persons were present who had met her in society in Brussels; but none suspected the truth--I alone held her secret. When later that night we bade each other farewell at Waterloo Station, she managed to whisper, "I shall be at Fedor's on Thursday night at nine. Meet me there. Do not fail." "Very well," I replied; and, allowing her well-gloved hand to rest in mine for a moment, she bade me _au revoir_, entered a cab, and was driven away. ------------------------------------------------------------------------ As I walked into Fedor Nikiforovitch's handsomely-furnished drawing-room at Sydenham to keep my appointment, my host rose to greet me. He was tall, thin and slightly bent by age. In Warsaw I had known him as an active revolutionist, and, indeed, the men who were with him-- Tchartkoff, Petrovitch, and Karamasoff--were a trio of daring fellows, who, alone and unaided, had committed many startling outrages. Several others were in the room, and among them I noticed two ladies, Mascha Karelin and Vera Irteneff, whom I had frequently met at secret meetings of the Circle at Warsaw. "Sonia told me you were coming," Fedor said gayly. "This is the final council. The attempt will be made to-morrow," he added in a whisper.